﻿using System;
using System.Web;
using System.Drawing;
using System.Security.Cryptography;

/// <summary>
/// 验证码类
/// </summary>
public class Rand
{
    #region 生成随机数字
    /// <summary>
    /// 生成随机数字
    /// </summary>
    /// <param name="length">生成长度</param>
    public static string Number(int Length)
    {
        return Number(Length, false);
    }

    /// <summary>
    /// 生成随机数字
    /// </summary>
    /// <param name="Length">生成长度</param>
    /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>
    public static string Number(int Length, bool Sleep)
    {
        if (Sleep) System.Threading.Thread.Sleep(3);
        string result = "";
        System.Random random = new Random();
        for (int i = 0; i < Length; i++)
        {
            result += random.Next(10).ToString();
        }
        return result;
    }
    #endregion
   
    #region 生成随机字母与数字
    /// <summary>
    /// 生成随机字母与数字
    /// </summary>
    /// <param name="IntStr">生成长度</param>
    public static string Str(int Length)
    {
        return Str(Length, false);
    }

    /// <summary>
    /// 生成随机字母与数字
    /// </summary>
    /// <param name="Length">生成长度</param>
    /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>
    public static string Str(int Length, bool Sleep)
    {
        if (Sleep) System.Threading.Thread.Sleep(3);
        char[] Pattern = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
        string result = "";
        int n = Pattern.Length;
        System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));
        for (int i = 0; i < Length; i++)
        {
            int rnd = random.Next(0, n);
            result += Pattern[rnd];
        }
        return result;
    }
    #endregion

    #region 生成随机纯字母随机数
    /// <summary>
    /// 生成随机纯字母随机数
    /// </summary>
    /// <param name="IntStr">生成长度</param>
    public static string Str_char(int Length)
    {
        return Str_char(Length, false);
    }

    /// <summary>
    /// 生成随机纯字母随机数
    /// </summary>
    /// <param name="Length">生成长度</param>
    /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>
    public static string Str_char(int Length, bool Sleep)
    {
        if (Sleep) System.Threading.Thread.Sleep(3);
        char[] Pattern = new char[] { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
        string result = "";
        int n = Pattern.Length;
        System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));
        for (int i = 0; i < Length; i++)
        {
            int rnd = random.Next(0, n);
            result += Pattern[rnd];
        }
        return result;
    }
    #endregion
}

/// <summary>
/// 验证图片类
/// </summary>
public class YZMHelper
{
    #region 私有字段
    private string text;
    private Bitmap image;
    private int letterCount = 4;   //验证码位数
    private int letterWidth = 16;  //单个字体的宽度范围
    private int letterHeight = 20; //单个字体的高度范围
    private static byte[] randb = new byte[4];
    private static RNGCryptoServiceProvider rand = new RNGCryptoServiceProvider();
    private Font[] fonts = 
    {
       new Font(new FontFamily("Times New Roman"),10 +Next(1),System.Drawing.FontStyle.Regular),
       new Font(new FontFamily("Georgia"), 10 + Next(1),System.Drawing.FontStyle.Regular),
       new Font(new FontFamily("Arial"), 10 + Next(1),System.Drawing.FontStyle.Regular),
       new Font(new FontFamily("Comic Sans MS"), 10 + Next(1),System.Drawing.FontStyle.Regular)
    };
    #endregion

    #region 公有属性
    /// <summary>
    /// 验证码
    /// </summary>
    public string Text
    {
        get { return this.text; }
    }

    /// <summary>
    /// 验证码图片
    /// </summary>
    public Bitmap Image
    {
        get { return this.image; }
    }
    #endregion

    #region 构造函数
    public YZMHelper()
    {
        HttpContext.Current.Response.Expires = 0;
        HttpContext.Current.Response.Buffer = true;
        HttpContext.Current.Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);
        HttpContext.Current.Response.AddHeader("pragma", "no-cache");
        HttpContext.Current.Response.CacheControl = "no-cache";
        this.text = Rand.Number(4);
        CreateImage();
    }
    #endregion

    #region 私有方法
    /// <summary>
    /// 获得下一个随机数
    /// </summary>
    /// <param name="max">最大值</param>
    private static int Next(int max)
    {
        rand.GetBytes(randb);
        int value = BitConverter.ToInt32(randb, 0);
        value = value % (max + 1);
        if (value < 0) value = -value;
        return value;
    }

    /// <summary>
    /// 获得下一个随机数
    /// </summary>
    /// <param name="min">最小值</param>
    /// <param name="max">最大值</param>
    private static int Next(int min, int max)
    {
        int value = Next(max - min) + min;
        return value;
    }
    #endregion

    #region 公共方法
    /// <summary>
    /// 绘制验证码
    /// </summary>
    public void CreateImage()
    {
        int int_ImageWidth = this.text.Length * letterWidth;
        Bitmap image = new Bitmap(int_ImageWidth, letterHeight);
        Graphics g = Graphics.FromImage(image);
        g.Clear(Color.White);
        for (int i = 0; i < 2; i++)
        {
            int x1 = Next(image.Width - 1);
            int x2 = Next(image.Width - 1);
            int y1 = Next(image.Height - 1);
            int y2 = Next(image.Height - 1);
            g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
        }
        int _x = -12, _y = 0;
        for (int int_index = 0; int_index < this.text.Length; int_index++)
        {
            _x += Next(12, 16);
            _y = Next(-2, 2);
            string str_char = this.text.Substring(int_index, 1);
            str_char = Next(1) == 1 ? str_char.ToLower() : str_char.ToUpper();
            Brush newBrush = new SolidBrush(GetRandomColor());
            Point thePos = new Point(_x, _y);
            g.DrawString(str_char, fonts[Next(fonts.Length - 1)], newBrush, thePos);
        }
        for (int i = 0; i < 10; i++)
        {
            int x = Next(image.Width - 1);
            int y = Next(image.Height - 1);
            image.SetPixel(x, y, Color.FromArgb(Next(0, 255), Next(0, 255), Next(0, 255)));
        }
        image = TwistImage(image, true, Next(1, 3), Next(4, 6));
        g.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, int_ImageWidth - 1, (letterHeight - 1));
        this.image = image;
    }

    /// <summary>
    /// 字体随机颜色
    /// </summary>
    public Color GetRandomColor()
    {
        Random RandomNum_First = new Random((int)DateTime.Now.Ticks);
        System.Threading.Thread.Sleep(RandomNum_First.Next(50));
        Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);
        int int_Red = RandomNum_First.Next(180);
        int int_Green = RandomNum_Sencond.Next(180);
        int int_Blue = (int_Red + int_Green > 300) ? 0 : 400 - int_Red - int_Green;
        int_Blue = (int_Blue > 255) ? 255 : int_Blue;
        return Color.FromArgb(int_Red, int_Green, int_Blue);
    }

    /// <summary>
    /// 正弦曲线Wave扭曲图片
    /// </summary>
    /// <param name="srcBmp">图片路径</param>
    /// <param name="bXDir">如果扭曲则选择为True</param>
    /// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高,一般为3</param>
    /// <param name="dPhase">波形的起始相位,取值区间[0-2*PI)</param>
    public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
    {
        double PI = 6.283185307179586476925286766559;
        Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
        Graphics graph = Graphics.FromImage(destBmp);
        graph.FillRectangle(new SolidBrush(Color.White), 0, 0, destBmp.Width, destBmp.Height);
        graph.Dispose();
        double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;
        for (int i = 0; i < destBmp.Width; i++)
        {
            for (int j = 0; j < destBmp.Height; j++)
            {
                double dx = 0;
                dx = bXDir ? (PI * (double)j) / dBaseAxisLen : (PI * (double)i) / dBaseAxisLen;
                dx += dPhase;
                double dy = Math.Sin(dx);
                int nOldX = 0, nOldY = 0;
                nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
                nOldY = bXDir ? j : j + (int)(dy * dMultValue);

                Color color = srcBmp.GetPixel(i, j);
                if (nOldX >= 0 && nOldX < destBmp.Width
                 && nOldY >= 0 && nOldY < destBmp.Height)
                {
                    destBmp.SetPixel(nOldX, nOldY, color);
                }
            }
        }
        srcBmp.Dispose();
        return destBmp;
    }
    #endregion
}